Typically, electrically resistive strips employed in high-temperature electrical furnaces are formed as ribbons or helical coils. The ribbon or coil is supported by a base or support structure. The ribbon or coil may be entirely embedded within the base, or it may be supported in channels and grooves in the base. The conventional heaters having a coil or a ribbon embedded in the base are limited with respect to the speed with which the temperature can be changed. The thermal inertia of the base affects the efficiency of such a conventional heater, insofar as the heat must saturate the base material before direct radiation to the product can occur. In addition, because the coil or ribbon is supported in an open groove, the base material effectively obstructs a substantial portion of the direct radiation emitted by the coil or ribbon, thereby considerably reducing thermal efficiency.
Another prior art high-temperature heater employs a helically wound coil of wire supported continuously along its full length by an anchor of electrically-insulative, high-strength, high-thermal conductivity material embedded in a base support structure. Approximately one third of the coil is hidden in the anchor, and thus it cannot radiate. Further, the part of the coil embedded within the anchor is constrained against thermal expansion and contraction, which leads to coil fatigue. Also, the portion of the coil embedded in the anchor tends to undesirably react with the anchor material.